If you’ve ever had an imaginary argument in your head, you may have “heard” two voices at once. Your own inner voice and that of the other in the fight. You can even “hear” the other person’s accent, or the timbre of their voice.
So what’s happening in the? brain when that inner monologue runs? How come you can ‘hear’ your thoughts?
It turns out that the brain undergoes similar processes when you think words as when you speak out loud.
Inner monologues are thought to be a simulation of overt speech, said Hélène Loevenbruck, a senior neurolinguistics researcher and head of the language team in the Psychology and NeuroCognition Laboratory at CNRS, France’s national research institute. As children, we are virtual sponges, soaking up new information from every angle. Children who play alone often speak a dialogue aloud, for example between a toy truck and a stuffed animal. About 5 to 7 years old (opens in new tab)that verbalization moves inward, Loevenbruck said.
previous studies (opens in new tab) have shown that the brain exhibits similar activity with inner speech as with verbal speech. When study participants are asked to deliberately “speak” in their heads while lying in a magnetic resonance imaging (MRI) machine, scientists can see parts of the brain that process auditory information activated as if the participant actually hears the words.
“Cerebral regions activated during inner speech are very similar to those activated during overt speech during real speech,” Loevenbruck told Live Science. Those regions include the frontal lobe of the left hemisphere and the parietal lobe, which help process external stimulation.
But when you think of something like a fictitious argument with another person, the brain goes one step further. During that inner quarrel, you play two roles: yourself and the person you are arguing with. When you play yourself, the auditory centers on the left side of your brain are activated, Loevenbruck said. But when you switch roles internally to play the person you’re arguing with, “there’s kind of a shift of activation from the brain region to the right hemisphere,” she continued. If you look at the situation from a different perspective, even if it’s a perspective you’re making in your head, it shifts which areas of the brain are involved.
Researchers have also observed this phenomenon when participants are asked to imagine movement, Leovenbruck continued. For example, dancers use a different part of their brains to imagine dancing versus someone else dancing, a study published in the August issue of the journal cerebral cortex (opens in new tab) found it.
It’s one thing to see those areas of the brain activate when someone is told to think something, but it’s much less understood what happens in our brains when we let our minds wander, Leovenbruck said. Not all inner monologues are intentional. Sometimes words or sentences just pop into your head for no reason.
This phenomenon may have something to do with the brain’s “default mode network” (DMN), said Robert Chavez, a neuroscientist at the University of Oregon. The DMN is a network of areas in the brain that are active when not doing a specific task. The DMN is thought to be involved in aspects of internal thinking, such as retrieving memories, envisioning the future, or interoception — a sense or “feel” of what’s going on in your body, such as hunger or thirst.
“The default mode network seems to be more active when your mind wanders,” Chavez told Live Science. Because the default mode network involves planning for the future by drawing on memories, recent experiences, and mental associations, this combination of activities is thought to gives rise (opens in new tab) to an internal monologue as you turn inward.
Much more research is needed to understand how inner thoughts arise spontaneously, Leovenbruck said. When taken to extremes, inner thoughts can become dysfunctional, such as ruminating after an uncomfortable or traumatic event, or in mental disorders, such as schizophrenia, where people hear auditory hallucinations.
Originally published on Live Science.
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